In the related art, in a cooling system for cooling, for example, an internal combustion engine such as an automobile engine, a fluid control valve which is provided in a circulation flow path for circulating cooling water through the internal combustion engine and a heater core for heating by a water pump is known (for example, see JP 2015-121247A (Reference 1)). The fluid control valve of Reference 1 is known as a fluid control valve including a valve seat which has a plate-like first magnetic body (fixed yoke in the Reference) insert-molded in a housing, a valve body which has a plate-like second magnetic body (strip member in the Reference), and a solenoid which causes a magnetic flux to flow through the first magnetic body. The fluid control valve is provided with a biasing member (coil spring in the Reference) which biases the valve body toward a valve seat side.
In the fluid control valve of Reference 1, the water pump is stopped when the engine is stopped and the valve body is in a valve closed state by a biasing force of the biasing member. When the engine is started, the water pump is driven and a water pressure acts on the valve body. However, the valve body is pressed against the valve seat and the valve closed state is held by a driving force by energization of the solenoid and the biasing force of the biasing member. When heating is used after the engine is started, the energization of the solenoid is released, and when the water pressure acting on the valve body exceeds the biasing force of the biasing member, the valve body is separated from the valve seat and is in an valve opened state, and thus cooling water flows through the heater core.
In the fluid control valve of the related art, the valve closed state is maintained until the water pressure exceeds the biasing force of the biasing member even when the solenoid is not energized. Therefore, when the water pressure is low at a time of starting of the engine, for example, in a case where there is a request to supply cooling water from a defroster, the heater core, an EGR cooler, or the like, there is a concern that the valve cannot be opened promptly. In addition, since the valve is always in the valve closed state when the engine is stopped, the valve body and the valve seat are fixed, and even if it is attempted to open the valve promptly after starting the engine, there is a concern that it is difficult to open the valve.
On the other hand, when the valve is in the valve opened state, even if the solenoid is energized, the valve is not closed until a sum of the driving force of the solenoid and the biasing force of the biasing member exceeds the water pressure. Therefore, in a case where it is desired to promote warm-up and perform heating when an engine speed is low, or the like, there is a concern that the valve cannot be closed promptly.
Thus, a need exists for a fluid control valve which is not susceptible to the drawback mentioned above.